The need to protect a substrate from harmful environmental influences arises in many areas of technology. One general solution to the problem comprises surrounding the substrate with an appropriate encapsulant.
For instance, when the substrate region to be protected comprises a joint or splice between electrical cables, such as multiconductor communications cables of the type used in telephone systems, a prior art technique comprises providing an enclosure around the splice work, securing the enclosure to each cable entering the enclosure, and filling the enclosure with an insulating liquid curable encapsulant. The enclosure obviously has to be sufficiently leak-tight to prevent substantial loss of encapsulant during the time the encapsulant remains liquid.
In prior art systems of this type the encapsulant is universally introduced by pouring it into the enclosure under gravity. The encapsulant is thus essentially at ambient pressure. It flows to fill voids and interstices, but, being relatively viscous, does not penetrate far, if at all, into the cable ends. Also, trapped air pockets and other voids tend to remain. The main function of the encapsulant generally being protection of the conductors against contact with water, it is easily seen that such imperfections may tend to impair the effectiveness of the encapsulant. Water can enter a splice region through an enclosure imperfection or through one of the cables, in the latter case travelling from a point of damaged cable sheathing, along the conductors, to the splice region. Thus, encapsulant that does not, or does only to a limited extent, penetrate into the cable ends and/or interstices within the splice work, may not provide a sufficiently effective protection against water damage to the splice.
In a particular prior art system, a plastic liner is placed around the splice work and secured to the cables, thereby forming an enclosure into which liquid encapsulant is poured under gravity. The encapsulant in the enclosure is pressurized to some degree by wrapping ties, tape or the like, around the enclosure. In such a system, any encapsulant volume change subsequent to the wrapping leads to a change in pressure. For instance, flow of encapsulant into voids within the splice work, or into the cables, decreases the effective volume of encapsulant within the enclosure, and results in a loss of pressure. Furthermore, in such a system, the splice work is being compacted by the pressurizing means.
Since encapsulation is widely used, especially in the telecommunications industry, an approach that substantially retains the advantages of the prior art approach, e.g., convenience, re-enterability, and economy, while increasing the effectiveness of encapsulant in preventing water-induced damage to the substrate, would be of considerable interest. This application discloses such an approach.
The above-described approach to protecting a substrate is not the only one known to the art. For instance, U.S. Pat. No. 3,466,384 discloses a cable joint enclosed by an impermeable sleeve. And U.S. Pat. No. 4,209,352 discloses a method for sealing a closure member to a substrate using an inflatable bag or the like.